The use of an O.sub.2 sensor to sense the amount of O.sub.2 in the exhaust of an automobile or other motor vehicle and to send sensor signals to an electronic control unit or module (ECU) also incorporated in the motor vehicle is well known. The terms "electronic control unit", "module", "electronic control module" and "ECU" are used interchangeably herein. The ECU is associated with the fuel injector system of the engine to control the air/fuel mixture introduced into the engine cylinders. With the fuel system in closed loop operation after the O.sub.2 sensor warms up, the voltage of the O.sub.2 sensor voltage cycles up and down. This cycling (which varies in speed between idling and cruising) occurs because the ECU senses the O.sub.2 voltage and then changes the pulse width of the signal driving the fuel injector on and off. This switching action allows the ECU to perform minor adjustments to the air/fuel ratio to allow the catalytic converter to perform its job to optimize the "oxidation" of carbon monoxide and hydrocarbons as well as the reduction of nitrogen oxides. The oxidation occurs when the mixture is slightly lean and more oxygen is available, and the reduction occurs when the mixture is slightly rich and less oxygen is available.
It is known to modify the function of an existing electronic control unit or module (ECU) by physically changing the functional parameters of the programmable eprom or computer chip, or changing the existing eprom itself inside the ECU, in an effort to improve engine performance.
Various problems can arise when an existing ECU is modified as indicated above. The physically changed or new eprom must be specific to a manufacturer's application, and during use it may cause knocking, lean misfires, uncontrolled parameters during timed sequences and the signalling of alarming trouble codes in vehicles with on-board diagnostic (OBD) systems.
The following United States patents are known: U.S. Pat. No. 5,836,153, issued Nov. 17, 1998, U.S. Pat. No. 5,777,204, issued Jul. 7, 1998, U.S. Pat. No. 4,479,464, issued Oct. 30, 1984, U.S. Pat. No. 4,202,301, issued May 13, 1980, U.S. Pat. No. 5,033,438, issued Jul. 23, 1991, and U.S. Pat. No. 5,251,604, issued Oct. 12, 1993. As indicated above, the present invention utilizes a controller which is a separate component which is utilized with existing O.sub.2 sensors and ECUs. The controller does not physically modify, change or replace the functional parameters of the existing eprom or computer chip inside the ECU in any way and it has a universal "closed loop" application. The above-identified patents do not disclose or suggest such an arrangement.